Sori in stems and leaves (then mostly in the midrib), extended and coalescing, covered by a layer of host epidermal tissue that splits and peels back irregularly to expose the spores. Spore mass black, firm to somewhat granular, not strongly coherent.
Ustilospores (13-) 14.5-16 (-18.5) x 10-) 11-14.5 (-16) µm, rather irregular in form, globose to subglobose or ellipsoidal, with a round to polygonal outline, dark brown, almost opaque, the wall 1.5-2 µm thick, smooth, appearing two-layered in immature spores.
Not formally assessed, but listed as Extinct in GBI by Evans et al. (2006). It was last recorded in 1931.
In stems and leaves of Linaria vulgaris.
The following is taken from the account of the first GB record, from Glyndyfrdwy in VC48 Merioneth (Trans. Br. mycol. Soc. 2: 6-7, 1902): "The foliage of the Linaria which had not flowered looked chlorotic, to use a medical phrase that fits the condition exactly. A closer examination of these yellowish-green shoots shewed that both stem and leaves presented slatey coloured streaks that were evidently well within the tissues. On placing sections beneath the microscope the cause of this was shewn to be numerous dark brown spores arranged in groups around the long axis of the stem and the midrib of the leaves. Some underground shoots, bIanched through lack of sunlight, shewed the same slatey colour from the same cause, though in less degree."
In GBI, reported from VC29 Cambridgeshire (apparently without voucher material), VC48 Merioneth (given as VC50 Denbighshire in the original publication) and VC51 Flintshire (Prestatyn).